1. Field of the Invention
This invention relates to illumination control systems and, in particular, solid state illumination control systems using illumination amplifiers.
2. Description of the Prior Art
Control of illumination has been accomplished in the prior art with mechanical devices. The well known aperture and shutter of a camera are common mechanical devices for controlling light. Other prior art illumination control arrangements are described hereafter.
In the photoplotter field, a photohead is used to control light for exposing film. Mechanically positioned filters and shutters are used for illumination control such as described in U.S. Pat. No. 3,330,182 issued in July 1967.
In the construction field; mechanical devices such as shutters, louvres, shades, and awnings are used to control natural illumination. These devices may be fixed or mechanically controlled, but are not provided with electronic control capability.
In the computer field, electronic computers are in wide scale use. Illumination signals must be converted to electronic form for processing in prior art systems because of the absence of illumination computer devices for processing illumination signals.
In the display field, liquid crystal displays require external light, either dependent on ambient light or using light bulbs. Integral illumination sources have not been available for such displays.
Liquid crystal displays provide only fully on or fully off conditions, but do not provide analog or proportional control. Limitations of on-off control arrangements have severely limited applicability of liquid crystal devices. Also, because servo control is related to proportional control, servo control of illumination has not been feasible.